Seabed drilling fluid diverter nearing construction stage
With the addition of a free standing pro duction riser, the SWF diverter could easily be modified to perform as a tophole riserless drilling system. [30,315 bytes] The shallow water flow (SWF) diverter joint industry project (JIP) is moving toward construction of a prototype, following completion of design. The founding companies of the SWF diverter JIP - Amoco, Chevron, and Conoco - selected ABB/Vetco Gray to build the first SWF diverter.
Solution for deepwater sub-seabed flows
- With the addition of a free standing pro duction riser, the SWF diverter could easily be modified to perform as a tophole riserless drilling system. [30,315 bytes]
Project development has taken most of the group's initial $300,000 budget and over a year of time. JIP Administrator Alan Gault, a senior staff engineer with Conoco, said all the necessary work has been completed and construction is nearing.
The SWF diverter is designed to allow an operator to regulate the back-pressure on the formation while drilling through shallow water flow zones. The device fits on top of the low-pressure well housing and has chokes that can be opened or closed via a remotely operated vehicle (ROV). By regulating the pressure at the wellhead via the chokes, the operator can control the down hole pressure.
Rotating headThe key component to this modular tool is the subsea rotating head. This device makes the diverter a versatile tool with applications beyond its driving goal of overcoming SWF problems. Gault said with the addition of a freestanding return riser to transport returns to the surface from the subsea wellhead and the addition of a mud lift device (gas lift, pumping, etc.) the diverter could perform the function of a tophole riserless drilling system with the same benefits of a disposable mud system. This freestanding riser technology exists and could be integrated into the system with relatively little difficulty. In fact, it is this application that is generating some interest from operators in the North Sea.
While riserless drilling might be a practical application of this development, the scope of the current project is not that far reaching. Gault said the JIP has completed its mandate of designing the diverter and is currently seeking funding partners for the construction of the actual tool. He said costs to date are about $500,000.
That figure includes $210,000 from the JIP and contributory funds from ABB/Vetco Gray, Oceaneering, and Swaco. Vetco Gray and their subcontractors provided the matching funds as part of an agreement that states they will own the technology and provide the service.
As Gault explains, the SWF Diverter will not be built and sold as a product. The tool will come to market as a call-out service. Operators will contract for the tool as they would with any other service item.
The JIP participants, including ABB/Vetco Gray, will receive a royalty on the rental of the system over several years to recover their initial investment. The JIP partners will also receive priority use of the system. Gault said the majors who put together the JIP are interested in the tool being available, but are not in the oil service business so it makes since for them to fund it but not market it.
ConstructionThe JIP initially considered bids from four contractors before selecting ABB/Vetco Gray. Once selected, ABB elected to match the funds put up for the project by the partners in exchange for ownership of the technology. ABB did some preliminary engineering work in order to determine the cost and schedule for construction of a prototype tool. In addition to the cost/schedule, contracts were prepared for JIP participation and with the lead contractor ABB/Vetco Gray for the commercial development of the SWF Diverter system.
According to the project schedule, the prototype diverter could be built in 13 months for a total cost of $2.15 million, including the $500,000 already spent by ABB and the JIP partners.
To complete the project ABB/Vetco Gray will need to perform the detailed engineering work and the construction. ABB has subcontracted Oceaneering and Swatco on this project.
To complete the project, the JIP is currently soliciting further participation from the industry to raise the needed funds (around $940,000) to complete the project. Gault said he has been encouraged by interest not only from the major Gulf of Mexico players, but also from operators in the North Sea.
He said the JIP is looking for an additional eight or nine participants to put up $120,000 each to complete the project. Over-subscriptions to the JIP will result in reducing the financial obligations of the participants.
John Rosso, Product Group Manager for drilling systems at ABB/Vetco Gray said the SWF diverter JIP is a good fit for the company's hardware technology and its philosophy about SWF containment. Rosso said that current ABB/Vetco Gray technology contains, but does not control SWF.
Moving to controlThe move from containment to control is an important one because it will minimize hole enlargement due to the SWF. The primary technologies at work in this system, the subsea rotating head, and hydraulic subsea latching technologies are both under development by ABB/Vetco Gray.
Rosso thinks the construction schedule could be accelerated, if desired by the participants, and completed in 8-10 months once the funding is in place. Rosso said ABB is in a position to market this device because it already handles call out programs for other products such as subsea wellheads. This service would operate on a similar basis. The client would rent the diverter, which would be used for about 15 days at the beginning of the well. The unit would include a consulting engineer from ABB, who has been trained in the protocol for using the system. Rosso said ABB/Vetco Gray is not interested in performing the drilling engineering work on these wells, but would provide expertise in operating the diverter system.
Interested parties who desire to examine the preliminary engineering designs can execute a confidentiality agreement with ABB/Vetco Gray. This will allow viewing the documents in detail. Those operators interested in participating in this JIP should contact Allen Gault [Tel: (281) 293-3338 or e-mail:email@example.com].
Copyright 1998 Oil & Gas Journal. All Rights Reserved.